What does Property Let means in VB? - properties

Question

I have often come across code that looks like this.
Public Property Get MyProperty() As String
MyProperty = m_MyProperty
End Property
Public Property Set MyProperty(ByVal value As String)
m_MyProperty = value
End Property
Or even:
Public Property Get MyProperty() As String
Return m_MyProperty
End Property
And I had never ever met with this.
Public Property Let MyProperty(ByVal value As String)
m_MyProperty = value
End Property
Is the Let keyword the same as Set ?
According to this post, it seems so.
Properties in VB
MSDN states:
Property Let Statement
Declares the name, arguments, and code that form the body of a Property Let procedure, which assigns a value to a property.
Property Set Statement
Declares the name, arguments, and code that form the body of a Property procedure, which sets a reference to an object.
In addition to it, as per MSDN definition:
Property
A named attribute of a control, field, or object that you set to define one of the object's characteristics (such as size, color, or screen location) or an aspect of its behavior (such as whether the object is hidden).
Object
Objects seen in a Microsoft Access database:
tables, queries, forms, reports, macros, and modules
objects that are defined by the system, such as the MSysObjects table
Objects seen in a Microsoft Access project:
objects stored in the Access project file: forms, reports, macros, and modules
objects stored in the Microsoft SQL Server database: tables, table properties (such as > - indexes, triggers, keys, constraints, defaults, rules, and user-defined data types), views, stored procedures, and database diagrams
objects defined by the system, such as the sysindexes table
Objects seen in both Access databases and Access projects:
data access pages, which are shortcuts (displayed in the Database window) to corresponding HTML files stored in the file system
information from another application, such as a chart (graph) or a drawing
Except that the context under which I have seen the Property Let Statement used, there is no Access or whatsoever else.
Thanks for the received comments. They guided me to MSDN, though I still can't get the meaning of the Let statement, apart that it might be interchangeable with the Set statement, as I see it.
Are they both really interchangeable?

Answer 1

You pretty much answered your own question.
As you can see from the MSDN docs, a Let declaration for a property is used to assign a value, i.e. to be used for any datatype except for objects (for which you would normally assign through Set anyway).
So, following the same logic, a Set declaration would be used if you want/need to be able to assign objects, and only objects (typed or not) to a property.
So, let's say you have:
Property Let MyFirstProperty(NewValue As String)
m_sMyFirstProperty = NewValue
End Property
Property Set MySecondProperty(NewValue As Object)
Set m_oMySecondProperty = NewValue
End Property
Then the following won't work:
' This won't work
MyFirstProperty = CreateObject("...")
' Neither will this
Set MyFirstProperty = CreateObject("...")
' Also, the following won't be allowed
MySecondProperty = "My new string"
But the following two statements will:
MyFirstProperty = "My new string"
Set MySecondProperty = CreateObject("...")
Note that you can have both a Let and Set declarations for the same property at the same time, depending on what you want to do:
You could handle objects being assigned to the property differently (through the Set declare) than for other datatypes (using the Let);
Or, if your internal variable for the property is a Variant, and you want to allow both objects and scalar values to be assigned to the property.
In short, then:
If you want to assign values to a property (everything but objects), add a Let handler for the property.
If you want to assign objets to a property, you'll need a Set handler for the property.